1. Technical Field
The present invention relates to a noise removing filter, and more particularly, to a method of manufacturing a noise removing filter, by which the noise removing filter may obtain high magnetic permeability so as to improve impedance characteristics by using a simple structure and process, thereby increasing the performance of the noise removing filter.
2. Description of the Related Art
Electronic devices such as digital televisions (TVs), smart phones, or notebook computers have been widely used in terms of data transmission/receiving functions in a high-frequency band. Also, in the future, it is expected that these information technology (IT) electronic products will be more frequently used not only as multi-functional products and complex products by connecting the products to each other via a universal serial bus (USE) or other communication ports, but also, as a single device.
In this case, in order to rapidly transmit and receive data, a frequency band is moved from a low frequency band of MHz band to a high frequency band of GHz such that data may be transferred through as large as possible amounts of internal signal lines.
When data is transmitted between a main device and a peripheral device in a high frequency of GMz band in order to transmit and receive a large amount of data, it is seriously difficult to smoothly process data due to signal delay and other noises.
Thus, there is a need for obtaining immunity of an electronic device in order not only to prevent the electronic device itself from acting as a noise source, but to also prevent malfunction of the electronic device from occurring due to external noise.
In order to overcome these problems, an IT electronic device includes anti-electron magnetic interference (EMI) components installed around connectors between the IT electronic device and peripheral devices. However, a typical anti-EMI component is a wound or stack type component, has a large chip size, and has low electrical properties, and thus, is used only in a predetermined portion or a limited portion such as a large area circuit board. Accordingly, there is a need for anti-EMI components that can meet the development of slimmed, miniaturized, complex, and multi-functional products.
Hereinafter, a typical anti-EMI coil component, that is, a typical common mode filter of a noise removing filter will be described in detail with reference to FIGS. 1 through 2C.
Referring to FIGS. 1 through 2C, a typical common mode filter includes a lower magnetic substrate 10, an insulating layer 20 that is disposed on the lower magnetic substrate 10 and in which primary coil patterns 21 and secondary coil patterns 22 are formed to be symmetrical in a vertical direction, and an upper magnetic body 30 disposed on the insulating layer 20.
In this case, the insulating layer 20 is formed on the lower magnetic substrate 10 by a thin film process in such a way that the primary coil patterns 21 and the secondary coil patterns 22 may be formed in the insulating layer 20. An example of the thin film process is disclosed in Japanese Patent Publication No. 1996-203737.
In addition, a first input lead pattern 21a for inputting electricity to the primary coil patterns 21 and a first output lead pattern 21b for outputting electricity from the primary coil patterns 21, and a second input lead pattern 22a for inputting electricity to the secondary coil patterns 22 and a second output lead pattern 22b for outputting electricity from the secondary coil patterns 22 are formed on the insulating layer 20.
In more detail, the insulating layer 20 includes a first coil layer including the primary coil patterns 21 and the first input lead pattern 21a, a second coil layer including the secondary coil patterns 22 and the second input lead pattern 22a, and a third coil layer including the first output lead pattern 21b and the second output lead pattern 22b. 
That is, the first coil layer is formed by forming the primary coil patterns 21 and the first input lead pattern 21a on an upper surface of the lower magnetic substrate 10 by a thin film process and then coating an insulating material on the resulting structure.
In addition, the second coil layer is formed by forming the secondary coil patterns 22 corresponding to the primary coil patterns 21 and the second input lead pattern 22a on an upper surface of the first coil layer by a thin film process and then coating an insulating material on the resulting structure.
Then, the third coil layer is formed by forming the first output lead pattern 21b and the second output lead pattern 22b on an upper surface of the second coil layer by a thin film process for external output of the primary coil patterns 21 and the secondary coil patterns 22 and then coating an insulating material on an upper surface of the second coil layer.
In this case, the primary coil patterns 21 and the secondary coil patterns 22 may be electrically connected to the first output lead pattern 21b and the second output lead pattern 22b through via connecting structures, respectively.
In addition, the first input lead pattern 21a is connected to a first input stud terminal 41a. The first output lead pattern 21b is connected to a first output stud terminal (not shown) corresponding to the first input stud terminal 41a. The second input lead pattern 22a is connected to a second input stud terminal 42a. The second output lead pattern 22b is connected to a second output stud terminal (not shown) corresponding to the second input stud terminal 42a. 
Although not illustrated in detail, the first coil layer through the third coil layer may each be prepared in the sheet form and may be combined with each other in a stacking manner so as to constitute an insulating layer including the first and secondary coil patterns 21 and 22, the first and second input lead patterns 21a and 22a, and the first and second output lead patterns 21b and 22b. 
In the above-described typical common mode filter, the upper magnetic body 30 is formed by filling a space with a composite material obtained by mixing ferrite with resin as a binder in order to increase adhesive properties with the insulating layer 20, insulating properties, and breakdown voltage properties. In this case, the magnetic permeability of the common mode filter seriously deteriorates due to the resin included in the upper magnetic body 30, thereby reducing the performance and characteristics of the common mode filter.
Thus, if ferrite having a large diameter is used in the upper magnetic body 30 in order to increase the magnetic permeability of the common mode filter, the high-frequency properties of the common mode filter deteriorates. If the amount of resin as a binder of the upper magnetic body 30 is reduced, adhesive properties with the upper magnetic body 30, and the insulating properties and breakdown voltage properties of the upper magnetic body 30 deteriorate.
In addition, in order to increase the magnetic permeability of the common mode filter, a high-temperature environment is provided during shaping of the upper magnetic body 30. However, processability can be reduced at a high temperature, facilities for increasing a temperature can be required, and the reliability of the common mode filter can be reduced.